What does it mean to live? What does it mean to love? What evidence do we have that we have a soul?

It’s not saying too much to say that those are the questions that have plagued mankind for millennia. And it’s not saying too much to say that we’re not much closer to an answer than when Socrates asked them over a cup of hemlock over all those years ago.

Shot in washed out and muted tones, all the better to suggest a postwar Britain world that is just like — but not entirely — our own, the film follows the story of three English young people — Kathy (Mulligan), Tommy (Garfield) and Ruth (Knightley).

Recounted through the eyes of an adult Kathy, the story follows the trio from their time as children at a remote boarding school in the English countryside called Hailsham (where they learn of their agonizing fate) through their 20s (as they try to understand and live with it) and to their ultimately tragic end.

An inspection of reviews from the time of the film’s theatrical release pretty well explains why these three children are doomed. But if you haven’t seen the movie or read Ishiguro’s masterful book, be warned: Serious spoilers ahead.

Kathy, Ruth and Tommy — along with all the other children at Hailsham — are “donors,” clones bred in a laboratory to serve as spare parts for their “originals” who live somewhere out in the wider world. They exist for one reason only: to someday give up their organs so that someone else can live. They’re less humans than kind of walking, talking consumer products. And at the end, they’ll die, or, in a horrifying euphemism “reach completion.”

The scene where the children learn of their fate — courtesy of a young teacher named Miss Lucy (Hawkins) is absolutely gut-wrenching. But she tells the children they need to know if they’re going to have “decent lives.” The stoicness with which the youngsters accept — even embrace — their fate is one of the most moving of the film. And it hits like a ton of bricks.

As they grow together, Kathy, Tommy and Ruth live lives that, again, are almost, but not entirely like our own.

At Hailsham, the students play act at ordering tea in a restaurant. There’s a schoolkids’ love-triangle between Ruth, Tommy and Kathy that has devastating consequences later on. And, as they move out into the wider world to begin their lives as donors, they inevitably grow apart, just like so many of us do with the childhood friends we once imagined we could never live without. And like so many of us, they rediscover each other later in life, when, for all practical purposes, it’s too late.

Mulligan brings a quiet strength to the dowdy Kathy, who spends her time before her inevitable end as a “carer” looking after donors going about their life’s work. There’s a haunted look that never leaves her eyes, suggesting the horror that she knows she will ultimately have to undergo herself.

Garfield’s Tommy never really shrugs off his adolescent awkwardness. He also owns one of the most harrowing scenes of the film, when the door to what he hopes will be an escape is slammed shut in front of him.

Knightley, as Ruth, brings the same glamourous detachment she brings to many of her roles. Emotions flit darkly across her finely boned face. And as she looks for one last shot of redemption, there’s echoes there of the purpose that all of us hope our lives will ultimately have.

Like the best science-fiction, “Never Let Me Go” forces the viewer to confront the big issues: What value does a life have, when, God knows, history is replete with examples of cultures valuing some lives above others? Can you transcend your circumstances or is your fate already etched on the wall of the universe?

Ultimately, the movie works best as a reminder that life — all life — is fleeting. And that life — all life — is precious and how we sometimes don’t realize that until it’s too late.